Field effect transistor including gate insulating layer formed of two-dimensional material
Provided is a field effect transistor including a gate insulating layer having a two-dimensional material. The field effect transistor may include a first channel layer; a second channel layer disposed on the first channel layer; a gate insulating layer disposed on the second channel layer; a gate electrode disposed on the gate insulating layer; a first electrode electrically connected to the first channel layer; and a second electrode electrically connected to the second channel layer. Here, the gate insulating layer may include an insulative, high-k, two-dimensional material.
1. A field effect transistor comprising:
a channel layer;
a gate insulating layer including an insulative, high-k, two-dimensional material on the channel layer;
a gate electrode on the gate insulating layer;
a first electrode electrically connected to the channel layer; and
a second electrode electrically connected to the channel layer,
wherein the channel layer comprises a semiconductor material having a two-dimensional crystal structure,
wherein the gate insulating layer comprises a ferroelectric material having a two-dimensional crystal structure,
wherein an interface charge density between the channel layer and the gate insulating layer is 1×10 12 per cm 2 or less,
wherein the field effect transistor has a subthreshold swing value of about 60 mV/dec or less.
2. The field effect transistor of claim 1 , wherein the gate insulating layer comprises at least one of an oxide nanosheet having a two-dimensional crystal structure, and a layered perovskite having a two-dimensional crystal structure.
3. The field effect transistor of claim 2 , wherein the gate insulating layer comprises the oxide nanosheet having the two-dimensional crystal structure, and the oxide nanosheet having the two-dimensional crystal structure comprises at least one of TiOx, TiNbOx, TiTaOx, NbOx, TaOx, LaNbOx, CaNbOx, SrNbOx, BaTaOx, WOx, and TiCoOx.
4. The field effect transistor of claim 2 , wherein the gate insulating layer comprises the layered perovskite having the two-dimensional crystal structure, and the layered perovskite having the two-dimensional crystal structure comprises at least one of LaNb2O7, LaEuNb4O14, EuTa4O14, SrTa2O7, Bi2SrTa2O9, Ca2Nb3O10, La2Ti2NbO10, Ba5Ta4O15, and W2O7.
5. The field effect transistor of claim 2 , wherein the gate insulating layer comprises the ferroelectric material having the two-dimensional crystal structure, and the ferroelectric material having the two-dimensional crystal structure comprises at least one of In2Se2, HfZrO2, and Si—HfO2.
6. The field effect transistor of claim 1 , wherein the gate insulating layer including the insulative, high-k, two-dimensional material comprises at least one of 1T-HfO2, 1T-ZrO2, 1T-GeO2, 1T-SnO2, 1T-TiO2, 1T-PtO2, 2H—GeO2, 2H—HfO2, 1T-HfS2, 1T-PdO2, 2H—ZrO2, 1T-PtS2, 2H—MoO2, 2H—WO2, and 1T-SnS2.
7. The field effect transistor of claim 1 , the channel layer comprises:
a first channel layer; and
a second channel layer on the first channel layer,
wherein the gate insulating layer is disposed on the second channel layer,
wherein the first electrode is electrically connected to the first channel layer, and
wherein the second electrode is electrically connected to the second channel layer.
8. The field effect transistor of claim 7 , wherein
the second channel layer comprises the semiconductor material having the two-dimensional crystal structure,
the second channel layer and the gate insulating layer are van-der-Waals bonded to each other.
9. The field effect transistor of claim 7 , wherein the first channel layer and the second channel layer comprise different semiconductor materials and are doped to have an electrically identical conductivity type.
10. The field effect transistor of claim 7 , wherein the first channel layer is doped to have a first conductivity type, and the second channel layer is doped to have a second conductivity type which is electrically opposite to the first conductivity type, and
wherein the first channel layer and the second channel layer comprise an identical semiconductor material.
11. The field effect transistor of claim 7 , wherein the gate insulating layer is disposed to cover a portion of an upper surface of the second channel layer.
12. The field effect transistor of claim 7 , wherein the gate insulating layer and the gate electrode protrude in a lateral direction toward the first electrode from a first edge of the second channel layer such that the gate insulating layer and the gate electrode extend onto an upper surface of the first electrode.
13. The field effect transistor of claim 7 , wherein the gate insulating layer and the gate electrode are disposed to protrude in a lateral direction toward the second electrode from a second edge of the second channel layer such that the gate insulating layer and the gate electrode extend onto an upper surface of the second electrode.
14. The field effect transistor of claim 7 , further comprising an insulator layer disposed between the first channel layer and the second channel layer.
15. The field effect transistor of claim 7 , further comprising:
a substrate which is insulative,
wherein the first channel layer is disposed on an upper surface of the substrate.
16. The field effect transistor of claim 15 , wherein
the second channel layer covers a portion of an upper surface of the first channel layer,
a portion of the second channel layer protrudes in a lateral direction toward the second electrode from an edge of the first channel layer, and
the portion of the second channel layer protruding towards the second electrode is spaced apart from the substrate.
17. The field effect transistor of claim 15 , wherein
the second channel layer covers a portion of an upper surface of the first channel layer,
a portion of the second channel layer protrudes in a lateral direction toward the second electrode from an edge of the first channel layer, and
the portion of the second channel layer protruding towards the second electrode contacts the upper surface of the substrate.
18. The field effect transistor of claim 15 , further comprising:
a first contact layer on the substrate in direct contact with the first channel layer; and
a second contact layer on the substrate in direct contact with the second channel layer.
19. The field effect transistor of claim 18 , wherein
the first electrode on the first contact layer, and
the second electrode on the second contact layer.
20. The field effect transistor of claim 15 , further comprising:
a lower gate insulating layer embedded in the substrate and contacting with a lower surface of the first channel layer; and
a lower gate electrode embedded in the substrate and contacting with a lower surface of the lower gate insulating layer,
wherein the lower gate insulating layer comprises an insulative, high-k, two-dimensional material.